This invention relates to fluid brake control systems, and while the invention is subject to a wide range of applications, a preferred embodiment of the invention will be particularly described as applied to a fluid brake control system having improved displacement control apparatus.
Fundamentally, air brake systems for interchange rail vehicles are of the displacement type in that a full service brake application, for example, is attained when pressure in an auxiliary reservoir is equalized with pressure after displacement of a piston in each of one or more brake cylinders of a vehicle upon application of the brakes, and an emergency application is attained by equalizing the pressures of both an emergency reservoir and the auxiliary reservoir with pressure of the brake cylinders in combination with use of an inshot valve to limit the rate of build-up of brake cylinder pressure when it is being supplied with fluid from the auxiliary reservoir and the emergency reservoir at the same time. This provides for the most uniform calibration of brakes, with adequate reserve for leakage of fluid, of all vehicles in a train and is currently obtained by well-known AB and ABD control valves.
An alternate form of braking has been used more particularly in passenger vehicle control valves, such as in the well-known D22-AR control valve (disclosed in New York Air Brake Instruction Pamphlet No. 5050-7). This type of a valve uses the displacement principle in the control of a relay valve, which in turn governs brake cylinder pressure. This is accomplished by equalizing the auxiliary reservoir pressure with the pressure of a displacement reservoir having a volume equal to brake cylinder piston displacement volume for a full service brake application, and by equalizing pressures of the auxiliary reservoir, the emergency reservoir, and the displacement reservoir for an emergency brake application. The relay valve is controlled by the displacement reservoir pressure to deliver fluid from one or more supply reservoirs to one or more brake cylinders. This maintains the brake cylinders at a predetermined pressure ratio relative to the pressure of the displacement reservoir.
An object of the present invention is to provide a fluid brake control system which substantially obviates one or more of the limitations and disadvantages of the described prior systems.
Another object of the present invention is to reduce the amount of air required for brake applications.
Another object of the present invention is to reduce the time required for the application and release of brakes of a vehicle.
Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings and in part pointed out as the description of the invention progresses.